African-Americans and Caucasians have similar emotional brain activity when
10 May 2005
Americans and Caucasians viewing African American faces display extremely
similar changes in the activity of brain structures that respond to emotional
events, a new UCLA study finds.
The changes occur in the amygdala, a
region of the brain that serves as an "alarm" to activate a cascade of other
biological systems to protect the body in times of danger, said Matthew D.
Lieberman, assistant professor of psychology at UCLA and lead author of the
The findings will be published May 8 in the online version of
Nature Neuroscience, and later in the print version.
Five out of eight
African Americans (63 percent) responded with significantly more amygdala
activity when presented with expressionless photographs of African Americans
than when they were shown expressionless photographs of Caucasians, Lieberman
and his colleagues found. Seven of 11 Caucasians (64 percent) in the study also
responded with greater activity in the amygdala when viewing the African
Although a third of participants in each race did
not show this effect, no participant in the study responded with greater
amygdala activity to the Caucasian photographs than to the African American
photographs, Lieberman said.
"We didn't see any differences in amygdala
activity between the racial groups," Lieberman said. "From looking at the
amygdala, you couldn't tell if the scans were from African American or Caucasian
"Many people of either race may not be happy to find out
that a part of their brain involved in responding to potential threats responds
more to African Americans than Caucasians," Lieberman said. "Even people who
believe to their core that they do not have prejudices may still have negative
associations that are not conscious."
Why do African Americans have
this amygdala response?
"One theory," Lieberman said, "is that
people are likely to pick up the stereotypes prevalent in a society regardless
of whether their family or community agrees with those stereotypes. Several
social psychologists have found evidence for this view. From an early age,
cultural views, media portrayals and even the body language of authority figures
may train our brains, whether we consciously agree or not."
research has shown that Caucasians show an increased amygdala response to
African American photos to the extent that they hold nonconscious negative
attitudes towards African Americans, Lieberman said.
Co-authors on the
study are Johanna Jarcho, a UCLA graduate student in Lieberman's laboratory;
UCLA graduate student Naomi Eisenberger; Susan Bookheimer, professor of
psychiatry and biobehavioral sciences at UCLA's David Geffen School of Medicine;
and Ahmad Hariri, assistant professor of psychiatry at the University of
Pittsburgh School of Medicine and a former UCLA graduate student.
researchers also studied whether adding a verbal label (such as "African
American") when viewing African American photos changes the amygdala response,
and found it does.
"When people look at an African American and think of
the word 'African American,' we no longer see the amygdala response," Lieberman
said. Instead, the researchers found changes in a second region of the brain:
the right ventrolateral prefrontal cortex. This region of the brain is located
behind the forehead and eyes, and has been associated with thinking in words
about emotional experiences; it also is associated with inhibiting behavior,
impulses and emotions.
"This region is especially active when you add
the verbal label to the face," Lieberman said. "The people who show the most
activity in the right ventrolateral prefrontal cortex show the least activity in
"We found that when the right ventrolateral prefrontal
cortex gets turned on, the amygdala does not," he added. "When you engage in
verbal labeling, that partially turns off or disrupts the amygdala response. The
right ventrolateral prefrontal cortex was significantly active only when people
were looking at African Americans and choosing the word 'African American.'"
These results suggest that "thinking about the race of others in words
may regulate some of the threat experienced when confronting unfamiliar or
feared others," Lieberman said. "It is possible this emotional 'benefit' of
using race-related words may have inadvertently contributed to the widespread
use of race-related words and stereotypes."
Lieberman and his colleagues
used functional magnetic resonance imaging (fMRI) to examine brain activity for
this study, conducted at UCLA's Ahmanson-Lovelace Brain Mapping Center.
The research was supported by the National Science Foundation and the
National Institute of Mental Health.